This invention relates generally to aircraft flight instruments and in particular to aircraft control position indicators (ACPI). During stall/spin tests conducted at NASA Langley Research Center, it became apparent that the existing aircraft control position indicators (ACPI) were inadequate. Such stall/spin tests are conducted in order to determine the flight characteristics of aircraft in spins entered into after stalling has occurred. While in the spin, the aircraft descends rapidly with a helical motion about its spin axis. These tests subject the pilot and the aircraft flight instruments to strong centrifugal and gravitational forces. The effect on the pilot is to make head and eye positioning difficult. The effect on the flight control indicators is to cause drift and other inaccuracies. The pilot in a spin test needs an instantaneous display of the exact position of the control surfaces in order to follow a predetermined flight plan and prevent drifting of the controls from their desired position. The display must be visible under all cockpit conditions and can require only a minimum of mental effort for its interpretation.
The gyro horizon devices currently used in aircraft are unsuitable for spin/stall tests. They provide the pilot with only an indirect indication of the positions of the aileron, elevator, and rudder control surfaces. These devices depend on gyroscopes mounted within the aircraft and are attitude indicators, in that they display the orientation of the aircraft relative to the natural horizon. The gyroscopes are adversely affected by the centrifugal forces and there is some lag between the actual attitude of the aircraft and the attitude as shown on the display. This type of device therefore does not allow rapid and precise repositioning of the control surfaces according to a test flight plan.
Another flight instrument experimented with was a mechanical edge-type meter. These meters have a display that includes a scale and a moving needle. The position of the needle on the scale indicates the position of the control surface over its range. This device is unsuitable because the needle tends to bounce as the aircraft flies and is subject to overshoot when the aircraft changes attitude.
It is therefore an object of this invention to provide an aircraft control position indicator (ACPI) that communicates to the pilot the instantaneous position of the major control surfaces with no tendency toward overshoot.
It is also the object of this invention to present the control surface position information in a manner so as to minimize the mental effort required for the pilot to interpret the display during complicated and stressful maneuvers.
It is a further object of this invention to provide an aircraft control position indicator that is not affected by gravitational and centrifugal forces.
Another object of this invention is to provide a means for rapidly and precisely repositioning aircraft controls according to a predetermined flight plan.
Still another object of this invention is to provide an aircraft flight instrument display that is visible to the pilot under all cockpit lighting conditions.
Other objects will be apparent from the detailed description when read with reference to the accompanying drawings.